On Tue, 22 Apr 2003, Markus Hofmann wrote:
Alex Rousskov wrote:
+ ICAP uses HTTP as transport; we can make
OCP look like ICAP/2.0, which may
significantly improve OCP survival/adoption
chances
Hm, does ICAP really use HTTP as transport, i.e. run on top of HTTP?
I'd say ICAP is a protocol that looks very much like HTTP and uses
TCP as the transport. Indeed, RFC 3507 states "ICAP uses TCP/IP as a
transport protocol. The default port is 1344, but other ports may
be used.".
Minor terminology conflict, I believe. When I said "HTTP transport", I
meant what you mean above. Since HTTP is so extensible, it is
difficult to say what is "transport" and what is "looks very much
like". If we use HTTP as (the only) OCP transport we are likely to do
what ICAP folks had to do or something similar to that.
An additional pro might be firewall traversal, although this might
not be that big of an issue in deployment scenarios OCP will play a
role (?).
Yes, though it becomes even less of an issue with firewalls becoming
smarter about the traffic they block (moving from L2-4 to L7).
Moreover, OCP servers, like ICAP servers, are not likely to run on
port 80 by default even if HTTP transport/model is used.
The kind of "streaming capabilities" of HTTP (i.e. chunking) is kind
of limited.
Yes, we would not be able to use chunking "as is" without giving up
current OCP flexibility to mix data chunks and control commands on the
same TCP connection.
If running over HTTP, would we expect problems with HTTP
intermediaries sitting in-between the OPES processor and the callout
server (for example if OPES processor and callout server ane in
different adminsitrative domains).
This question is on the to-do list: do we want OCP to be proxy-able?
We can probably go either way, especially if OCP is based on HTTP. At
this time, I see no reason to allow/document OCP proxies explicitly,
but once the transport protocol is selected, we must revisit the
issue.
I've never heard of BEEP proxies. Do they exist?
What about SOAP proxies? Are they similar to (or even the same as) XML
switches?
Alex.